QMIX [1]}:
QMIX introduces the monotonic constraint on the relationship between \(Q^{\operatorname{tot}}\)  and \(Q_i\) :
\(\frac{\partial Q^{\operatorname{tot}}(\tau , u)}{\partial Q_{i}(\tau _{i}, u_{i})} \ge 0, \forall i \in \lbrace 1,2, \ldots , N\rbrace  \nonumber \) 
